Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/01—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements
  • B01D29/05—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported
  • B01D29/07—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported with corrugated, folded or wound filtering sheets
  • B01D29/071—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements supported with corrugated, folded or wound filtering sheets with curved filtering elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/44—Edge filtering elements, i.e. using contiguous impervious surfaces
  • B01D29/445—Bar screens
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/62—Regenerating the filter material in the filter
  • B01D29/64—Regenerating the filter material in the filter by scrapers, brushes, nozzles, or the like, acting on the cake side of the filtering element
  • B01D29/6469—Regenerating the filter material in the filter by scrapers, brushes, nozzles, or the like, acting on the cake side of the filtering element scrapers
  • B01D29/6476—Regenerating the filter material in the filter by scrapers, brushes, nozzles, or the like, acting on the cake side of the filtering element scrapers with a rotary movement with respect to the filtering element
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/76—Handling the filter cake in the filter for purposes other than for regenerating
  • B01D29/80—Handling the filter cake in the filter for purposes other than for regenerating for drying
  • B01D29/82—Handling the filter cake in the filter for purposes other than for regenerating for drying by compression
  • B01D29/828—Handling the filter cake in the filter for purposes other than for regenerating for drying by compression using screws
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/76—Handling the filter cake in the filter for purposes other than for regenerating
  • B01D29/86—Retarding cake deposition on the filter during the filtration period, e.g. using stirrers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D33/00—Filters with filtering elements which move during the filtering operation
  • B01D33/01—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons
  • B01D33/03—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements
  • B01D33/0346—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements
  • B01D33/0353—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements self-supporting
  • B01D33/0361—Bar screens
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D33/00—Filters with filtering elements which move during the filtering operation
  • B01D33/01—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons
  • B01D33/03—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements
  • B01D33/0346—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements
  • B01D33/0353—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements self-supporting
  • B01D33/0369—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements self-supporting with curved filtering elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D33/00—Filters with filtering elements which move during the filtering operation
  • B01D33/27—Filters with filtering elements which move during the filtering operation with rotary filtering surfaces, which are neither cylindrical nor planar, e.g. helical surfaces
  • B01D33/275—Filters with filtering elements which move during the filtering operation with rotary filtering surfaces, which are neither cylindrical nor planar, e.g. helical surfaces using contiguous impervious surfaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D33/00—Filters with filtering elements which move during the filtering operation
  • B01D33/44—Regenerating the filter material in the filter
  • B01D33/46—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element
  • B01D33/466—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element scrapers

Definitions

• the present invention relates to a screw conveyor screen in accordance with the preamble of claim 1.
• Wastewater treatment plants accomplish removal of solid particles from the water to be clarified by way of screening.
• the water with solid particles is fed to the intake opening of the screen, said opening containing a rack through which the water entering the screen can flow out from the screen, while the screened solid matter remains on the rack and are subsequently removed by means of a conveyor.
• Bar screens with rakes are constructed from parallel aligned bars, with a rake tooth inserted in each opening. The screen is cleaned by moving the rake between the bars.
• traveling belt rack and chain screens the bars are replaced by endless belts with rack- or chain-like links which recirculate and simultaneously elevate the screened matter from the water stream.
• screw conveyor screens the screened matter accumulated on the rack bars is elevated from the water screen by means of the screw.
• the bars are generally aligned about the flight of the screw parallel with the axis of the screw shaft and thus form a semicircular cradle under the screw.
• prior-art screw conveyor screens the protection against screen clogging has been attempted by way of shaping the bars so that solid particles can readily escape through the openings between the bars.
• the bars can have, e.g., a triangular cross section, and they are aligned so that the angle subtended outward from the bars opens downward widening, while one straight side of the triangular bar is aligned facing the flight of the screw.
• Known constructions of screw conveyor screens are hampered by the fact that thin plastic foils so abundant today in sewer waters form a blanket between the screw and the bar cradle that rapidly clogs the screen. Removal of such foils requires the stopping of the screen operation and at least a partial dismantling of the screen.
• the invention is based on the idea of constructing the bar cradle of the screen from two interlaced bar cradles that are reciprocatingly movable with respect to each other.
• the screw conveyor screen according to the invention is characterized by what is stated in the characterizing part of claim 1.
• the invention provides outstanding benefits.
• the apparatus concerned in the invention has several benefits over conventional screen constructions.
• the mutual motion of the interlaced bars prevents the formation of a blanket from thin plastic films between the bars and the screw, because the reciprocating motion of the adjacent bars forms creases on the film blankets, whereby the flight of the screw can grab the blanket and remove it.
• the bars can be made of commercially available shaped bar materials, and they need not be massive, because stresses from clogging are nonexistent.
• the openings are maintained open very effectively, because the bars are kept in constant motion so that they expel all possible soloid matter from the spacings between the bars. Because slightly widening angles are formed in the openings between the bars in the downward direction radially outward from the center axis of the screw, solid matter cannot accumulate between the bars and thence block the openings. Due to the small dimensions of the reciprocating machinery of the bars in the axial direction of the screw, the apparatus according to the invention can be placed in, e.g., a wastewater channel, whereby the installation costs of the screen remain extremely low.
• Figure 1 shows in a partially sectional side view a screen according to the invention.
• Figure 2 shows in a partially sectional side the reciprocating machinery of the bar cradle.
• Figure 3 shows the screen viewed from its end in the direction of its longitudinal axis.
• Figure 4 shows section B-B of Fig. 1.
• the screen comprises a shaft 2 whose center line C forms the longitudinal axis of the screen.
• a properly pitched flight 4 Onto the shaft 2 is adapted a properly pitched flight 4.
• the circumference of the flight 4 is enclosed by a frame 18 of the screen and an intake trough 6.
• the upper part of the intake trough 6 has a feed inlet 5, below which are adapted two bar cradles, both aligned parallel to the shaft of the flight. Bars 7 and S of the cradles are mutually interlaced.
• a drive motor 1 is adapted to the upper end of the shaft 2, while the reciprocating elements 11 and 12 of the bar cradles are placed to the lower end of the shaft.
• the diameter of the flight 4 is large at the intake trough 6 and its diameter tapers smaller after the intake trough 6 and is continued as a smaller- diameter flight within the frame IS toward the upper end of the screen.
• a discharge outlet 3 is adapted to the upper end of the flight 4.
• the construction of the bar cradles is illustrated in Figs. 3 and 4.
• the bar cradle is formed by slat-shaped bars, namely slats 7 and 8.
• the slats 7 and 8 are placed parallel to the shaft 2 equidistantly spaced on a segment of an arch compliant with the perimeter of the flight 4.
• the slats 7, 8 have equal thickness and their long-side symmetry axes are aligned radially along the perimeter of the flight 4, whereby the each pair of adjacent slats 7 and 8 form an opening with a triangular cross section that widens toward the outside of the screen.
• Every second of the slats 7, 8 is a fixed slat 8, while every other second is a movable slat 7.
• the movable slats 7 are slightly longer than the fixed slats 8, and they are attached at their one end to an end support plate 9, which further is located between actuating disks 11 and 12.
• the bar cradle is stiffened by means of arched support beams 17 to the shape of the flight's perimeter.
• the end of the screen is provided at the intake trough 6 side with a permanently mounted stop plate 10 which prevents the entry of solid particles to the reciprocating machinery of the bar cradle (Fig. 2).
• the reciprocating machinery is adapted to the end of the shaft 2 and receives its actuating power via the shaft from a drive motor 1.
• the reciprocating machinery is comprised of two actuating disks 11 and 12 mounted onto the shaft.
• the disks 11, 12 are adapted with the help of bushings 13, 14 and 15 in an inclined position onto the shaft 2 with respect to the center line C of the shaft 2.
• One ends of the outermost bushings 13 and 15 are straight, while the other ends are inclined.
• Both ends of the bushing 14 between the actuating disks 11 and 12 are inclined.
• the actuating disks are placed between the bushings 13, 14 and 15 and fixed in place by means of a tightening nut 16.
• the apparatus described above operates as follows.
• the drive motor 1 rotates the flight 4 of the screw by the shaft 2.
• a liquid containing solids such as sludge enters the intake trough 6 via the feed inlet 5.
• the bar cradle comprised of the slats 7 and 8 performs the separation of solids from the liquid.
• the solid particles remain on the bar cradle, while the liquid is allowed to pass through the cradle out from the screen.
• the drive motor 1 rotates the flight 4 whose outer edge rests against the inner surface of the bar cradles 7 and 8.
• the flight transfers solid particles trapped on the surface of the bar cradle toward the discharge outlet 3 through which they are removed from the screen.
• the end support plate 9 placed to the end of the bar cradle formed by the movable slats 7 is moved in the direction of the shaft's center line C deflected by the inclined actuator plates 11, 12 and supported by the arched support beams 17. Resultingly, the bar cradle formed by the slats 7 is forced by the rotation of the shaft 2 to a reciprocating motion with respect to the stationary bar cradle formed by the slats 8.
• the openings between the slats 7, 8 remain consistently unclogged by virtue of their mutual movement, and the accumulation of blocking foils or other solid matter between the bar cradle and the flight is avoided.
• the actuating machinery can operate in such a manner that the shaft 2 has permanently fixed bushings 13 and 15, whereby a freely moving actuator plate with a diameter smaller than that described in the above embodiment is adapted onto the shaft 2 of the flight between said actuator plates.
• the actuating plate does not rotate with the shaft 2 of the flight, but instead, has a slotted hole at its lower end, whereby the end support 9 is flexibly mounted to the slotted hole.
• the actuating plates can also be mounted by other methods onto the shaft 2. e.g., by welding them to an inclined position onto the shaft, but the dismantling of such a screen construction becomes difficult.
• each bar cradle requires a separate actuating machinery which may be comprised of, e.g., several adjacent actuating disks, and correspondingly, end support plates adapted between the disks.
• the mutual motion of the slats can also be implemented so that the movable slats are pivotally fixed by joints at their one end to the frame of the screen, while their other end is fixed via an eccentric peg and slot mechanism or a crank mechanism to the shaft of the screen.
• This arrangement forces the slats to move radially with respect to the flight.
• Such a construction is more susceptible to damage than the approach using the longitudinally reciprocating motion, because particles capable of jamming the motion can more easily reach the openings between the slats.
• the actuating mechanism of the slats can alternatively be implemented, e.g., by providing the end of the shaft 2 with a crank driven via an eccentric and a slotted hole, said crank being pivotally fixed at its midpoint.
• the slotted hole at the other end of the crank is adapted to the slot in the end support plate.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Specific Sealing Or Ventilating Devices For Doors And Windows (AREA)
• Sewage (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8531433

Family Applications (1)

Country Status (3)

Cited By (4)

Citations (7)

• 1990
  • 1990-11-19 FI FI905712A patent/FI87186C/fi not_active IP Right Cessation
• 1991
  • 1991-11-18 WO PCT/FI1991/000342 patent/WO1992008539A1/en active Application Filing
  • 1991-11-18 AU AU88643/91A patent/AU8864391A/en not_active Abandoned

Patent Citations (7)

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